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People often display essentialist biases, which can lead them to underestimate within-species variability. This bias is espe- cially pronounced when traits are described as advantageous for survival. However, it is unclear whether this bias is limited to the specified trait or encompasses complex trait interactions. We used Markov Chain Monte Carlo with People (MCMCp) to analyze people’s representations of biological variability, using ladybeetles as a model species. Participants either re- ceived contextual information about the benefits of ladybeetle color for survival, or survival-irrelevant information. Overall, participants held consistent beliefs about ladybeetle features, but those with survival-relevant context produced lighter and larger ladybeetles; this difference was consistent with survey responses. However, we found no significant interaction be- tween MCMCp variability and essentialism scores, given our context manipulation. We discuss potential explanations for these results and highlight advantages of MCMCp for assess- ing biological variability, particularly when studying the devel- opment of essentialist biases. 

People often display essentialist biases, which can lead them to underestimate within-species variability. This bias is especially pronounced when traits are described as advantageous for survival. However, it is unclear whether this bias is limited to the specified trait or encompasses complex trait interactions. We used Markov Chain Monte Carlo with People (MCMCp) to analyze people’s representations of biological variability, using ladybeetles as a model species. Participants either received contextual information about the benefits of ladybeetle color for survival, or survival-irrelevant information. Overall, participants held consistent beliefs about ladybeetle features, but those with survival-relevant context produced lighter and larger ladybeetles; this difference was consistent with survey responses. However, we found no significant interaction be- tween MCMCp variability and essentialism scores, given our context manipulation. We discuss potential explanations for these results and highlight advantages of MCMCp for assess- ing biological variability, particularly when studying the development of essentialist biases. 

In two experiments (N = 179), we studied the effect of contextual similarity and training mode on new vocabulary learning. Adult participants were trained on blocks of items that were semantically similar, phonologically similar, or unrelated to one another. Each participant was trained through passive exposure, active comprehension, or active production of the new vocabulary. Exp 1 trained items in clusters of 9, whereas Exp 2 trained the same number of items in clusters of 3. Exp 2 also assessed delayed retention 48-72 hours after training. Results showed a robust and negative impact of semantic similarity and production mode on vocabulary learning. A detrimental effect of phonological similarity was only observed in the delayed test. These results suggest that adding the challenge of resolving similarity-induced competition and articulating the word-form negatively impacts the quick acquisition of new vocabulary.